Try go to about:config page, search for "plugin.state.flash" change its value to 1(Ask to active)

• about:config

Or try reinstall the flash player.

Thanks for the quick reply but It is set to 1.

Also the choice is missing for all my plugins not just the flash.

You can check if click-to-play in enabled: the plugins.click_to_play pref should be set to true on the about:config page

• https://support.mozilla.org/kb/why-do-i-have-click-activate-plugins
• http://kb.mozillazine.org/Issues_related_to_plugins#Click_to_Play

If you do not keep changes after a restart or otherwise have problems with preferences, see:

• http://kb.mozillazine.org/Preferences_not_saved
• http://kb.mozillazine.org/about:config

And to address one of the common reasons for Flash problems, try disabling the protected mode feature. In some configurations, this security feature can cause instability or hang Firefox with repeated dialogs about scripts not running well.

The following pages provide information on how to disable the protected mode feature.

• Adobe support article under the heading "Last Resort": Adobe Forums: How do I troubleshoot Flash Player's protected mode for Firefox?

• Manual steps: https://support.mozilla.org/questions/968190?page=5#answer-509209

• Batch file: https://support.mozilla.org/questions/982093#answer-518078

THANKS people!

Set plugins.click_to_play to true

and reinstalled flash and now my ask option is back for all plugins.

WEIRD.